Can Congress force itself to balance the books?

Congressman Barber B. Conable Jr., a conservative noted for choosing straight talk over political slogans, has lost his patience. During his 18 years in Congress, the upstate New York Republican has seen the federal budget balanced only once and the deficit grow to $100 billion-plus a year.

He says he no longer believes his colleagues will balance the budget, so he is leading the charge in the House for a constitutional amendment to make them.

''It's a moderate proposal,'' he says in an interview in which he defends the amendment against charges that it would it would create economic havoc, or else be ignored by lawmakers and thus be a hoax.

Representative Conable, who is the ranking Republican on the House Ways and Means Committee and one of the most knowledgeable lawmakers on tax and spending issues, explains that he began pushing for the amendment only recently, ''when I decided that it simply had to be done.''

He admittedly is coming in through the back door. One of his first concerns is to forestall a constitutional convention on a balanced-budget amendment, which 31 states, three short of the required number, have already called for.

Such a convention could open up the whole Constitution, he warns. ''We haven't had a constitutional convention since 1787, and I'm not convinced that there are a lot of Madisons, Jays, Hamiltons, Franklins, and Washingtons lurking out there.''

''The second thing is that I think we're awfully foolish if we don't use a short-term fiscal crisis of this sort to get some long-term reform in our procedures,'' he says.

The proposed amendment would not be a ''straitjacket,'' according to Conable. ''It has in it sufficient wiggle room so that all it does is create an assumption in favor of greater fiscal discipline,'' such as the required three-fifths vote of both Houses to approve a budget deficit except in time of war.

But if Congress, which recently approved a $104 billion deficit for the coming year, cannot now balance the budget, how could it succeed once the Constitution is changed?

''At least we're giving ourselves plenty of advance notice,'' he responds. ''The short-term risk that would come from trying to balance the budget this year is just too great, but we've got to understand that we can't go on like this. And that's one of the advantages also of the balanced budget amendment. It doesn't take effect until the second fiscal year after the ratification process.''

That could be some years away, since the amendment, if it wins a two-thirds majority in both Houses of Congress, must then win approval by 38 states.

Answering charges that the amendment would either damage the economy or else be circumvented by Congress, Conable says, ''I say we've struck an appropriate balance. The people who are afraid of this are not afraid it will do nothing. They're afraid it will do too much.''

Will the amendment do too much, especially to reduce the massive social security program as some critics say? The New York lawmaker bristles at the charge.

''Social security has got to be controlled not for budgetary reasons but to save the system,'' he says, adding that opponents who say otherwise are using ''sheer demagoguery.'' While social security growth would be restrained, so would defense spending and ''every element in the budget,'' he maintains.

Conable dismissed the widespread skepticism of economists on the amendment, saying, ''The only group that I can think of that has more to be humble about than economists is politicians.Politicians have reason to be humble because they've listened to the economists.''

''Economists always wanted to be able to flood the economy with money if there is a recession,'' he says, blaming the policy for government overspending.

Contrary to the opponents, Conable sees only positive effects from the amendment. ''It would stabilize the economy. It would reduce the wide swings in the economy that result in fiscal excess,'' he says.

On the chances for passage this summer, Conable is less optimistic than other congressional leaders, however. The Senate is expected to act soon on the amendment, but the process has slowed down as some senators fight for changes in the wording. As of this writing, the Senate had already approved some ''clarifying'' language proposed by Sen. Pete V. Domenici (R) of New Mexico.

''Delay is a disaster for an amendment of this type'' in an election year, says Conable, explaining that Congress will probably recess soon so members can go home to campaign.

Conable worries aloud that Senate changes would require a House-Senate conference, in which he points out that House members of such a conference would be appointed by a Democratic leadership that is hostile to the balanced budget amendment.